// Copyright © SixtyFPS GmbH <info@slint.dev>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0

import { CupertinoPalette, Icons } from "styling.slint";

export component ScrollBar inherits Rectangle {
    in property <bool> enabled;
    out property <bool> has-hover: touch-area.has-hover;
    in-out property <bool> horizontal;
    in-out property <length> maximum;
    in-out property <length> page-size;
    in-out property <length> value;
    in property <ScrollBarPolicy> policy: ScrollBarPolicy.as-needed;

    callback scrolled();

    property <length> track-size: root.horizontal ? root.width - 2 * root.offset : root.height - 2 * offset;
    property <length> step-size: 10px;
    property <length> offset: 2px;
    property <length> pad: 2px;

    background: transparent;
    visible: (self.policy == ScrollBarPolicy.always-on) || (self.policy == ScrollBarPolicy.as-needed && self.maximum > 0);
    clip: true;

    states [
        hover when touch-area.has-hover : {
            background: CupertinoPalette.foreground.with-alpha(0.2);
            border.background: CupertinoPalette.foreground.with-alpha(0.2);
            pad: 4px;
        }
    ]

    animate width, height, pad, background { duration: 150ms; easing: ease-out; }

    border := Rectangle {
        x: 0;
        y: 0;
        width: !root.horizontal ? 0.8px : parent.width;
        height: !root.horizontal ? parent.height : 0.8px;
        background: transparent;
    }

    thumb := Rectangle {
        width: !root.horizontal ? parent.width - 2 * root.pad : root.maximum <= 0phx ? 0phx : max(min(32px, root.width), root.track-size * root.page-size / (root.maximum + root.page-size));
        height: root.horizontal ? parent.height - 2 * root.pad : root.maximum <= 0phx ? 0phx : max(min(32px, root.height), root.track-size * (root.page-size / (root.maximum + root.page-size)));
        x: !root.horizontal ? (parent.width - self.width) / 2 : root.offset + (root.track-size - thumb.width) * (-root.value / root.maximum);
        y: root.horizontal ? (parent.height - self.height) / 2 : root.offset + (root.track-size - thumb.height) * (-root.value / root.maximum);
        border-radius: (root.horizontal ? self.height : self.width) / 2;
        background: CupertinoPalette.foreground;
        opacity: 0.6;
        border-width: 0.8px;
        border-color: CupertinoPalette.foreground-neg;

        animate width, height { duration: 100ms; easing: ease-out; }
    }

    touch-area := TouchArea {
        property <length> pressed-value;

        width: parent.width;
        height: parent.height;

        pointer-event(event) => {
            if (event.button == PointerEventButton.left && event.kind == PointerEventKind.down) {
                self.pressed-value = -root.value;
            }
        }

        moved => {
            if (self.enabled && self.pressed) {
                root.value = -max(0px, min(root.maximum, self.pressed-value + (
                    root.horizontal ? (touch-area.mouse-x - touch-area.pressed-x) * (root.maximum / (root.track-size - thumb.width))
                               : (touch-area.mouse-y - touch-area.pressed-y) * (root.maximum / (root.track-size - thumb.height))
                )));
                root.scrolled();
            }
        }

        scroll-event(event) => {
            if (root.horizontal && event.delta-x != 0) {
                root.value = max(-root.maximum, min(0px, root.value + event.delta-x));
                return accept;
            } else if (!root.horizontal && event.delta-y != 0) {
                root.value = max(-root.maximum, min(0px, root.value + event.delta-y));
                return accept;
            }
            reject
        }
    }
}

export component ScrollView {
    in property <bool> enabled: true;
    out property <length> visible-width <=> flickable.width;
    out property <length> visible-height <=> flickable.height;
    in-out property <length> viewport-width <=> flickable.viewport-width;
    in-out property <length> viewport-height <=> flickable.viewport-height;
    in-out property <length> viewport-x <=> flickable.viewport-x;
    in-out property <length> viewport-y <=> flickable.viewport-y;
    in property <ScrollBarPolicy> vertical-scrollbar-policy <=> vertical-bar.policy;
    in property <ScrollBarPolicy> horizontal-scrollbar-policy <=> horizontal-bar.policy;
    in property <bool> mouse-drag <=> flickable.interactive;

    // FIXME: remove. This property is currently set by the ListView and is used by the native style to draw the scrollbar differently when it has focus
    in-out property <bool> has-focus;

    callback scrolled <=> flickable.flicked;

    min-height: 50px;
    min-width: 50px;
    horizontal-stretch: 1;
    vertical-stretch: 1;
    preferred-height: 100%;
    preferred-width: 100%;

    flickable := Flickable {
        x: 2px;
        y: 2px;
        interactive: false;
        viewport-y <=> vertical-bar.value;
        viewport-x <=> horizontal-bar.value;
        width: parent.width - 4px;
        height: parent.height - 4px;

        @children
    }

    vertical-bar := ScrollBar {
        enabled: root.enabled;
        x: parent.width  - self.width;
        y: 0;
        width: self.has-hover ? 20px : 12px;
        height: horizontal-bar.visible ? parent.height - horizontal-bar.height : parent.height;
        horizontal: false;
        maximum:  flickable.viewport-height - flickable.height;
        page-size:  flickable.height;

        scrolled => {root.scrolled()}
    }

    horizontal-bar := ScrollBar {
        enabled: root.enabled;
        width: vertical-bar.visible ? parent.width - vertical-bar.width : parent.width;
        height: self.has-hover ? 20px : 12px;
        y: parent.height - self.height;
        x: 0;
        horizontal: true;
        maximum:  flickable.viewport-width - flickable.width;
        page-size:  flickable.width;

        scrolled => {root.scrolled()}
    }
}
